The present invention relates to a wind power installation comprising a rotor and a generator driven by the rotor for generating electric power. At least one rotor blade is mounted in a rotor hub so as to be displaceable about its longitudinal axis. The wind power installation comprises an auxiliary generator driven by the rotor for generating electric power for at least one consumer.
A wind power installation having a multi-stage generator is known from DE 102 33 589 A1, the entire contents of which is incorporated hereby by reference. Different generator stages which are selectively connected or disconnected are provided in the wind power installation for different wind speeds. The multiple stages of the generator are intended to make effective use of a wide range of different wind strengths for generating electricity.
An adjusting apparatus for rotor blades is known from DE 196 44 705, the entire contents of which is incorporated hereby by reference. In adjusting the rotor blades, same are brought into an angled position, the so-called flag position, at which the wind power installation comes to a standstill. The adjusting apparatus comprises an auxiliary generator which is installed in fixed inter-connection with the nacelle/rotor and which derives power from the rotational motion of the rotor relative the nacelle. The rotor blades are rotated directly into the flag position by the power thus derived.
An apparatus for adjusting the angle of attack of a rotor blade having an emergency current circuit is known from DE 100 09 472 C2, the entire contents of which is incorporated hereby by reference. The emergency current circuit comprises a permanent magnet generator which connects to the motors for adjusting the angle of attack such that same is set into the flag position after the emergency current circuit switches on. A high velocity to the rotor blades is hereby also achieved upon a high rotational speed to the rotor shaft.
A wind power installation providing contactless power transmission from a non-rotating part of the wind power installation to the rotor is known from DE 101 53 644 C2, the entire contents of which is incorporated hereby by reference. For this purpose, an asynchronous machine is integrated into the wind power installation, the stator of which is connected to the non-rotating part of the wind power installation and the rotor of which is arranged at the rotating part.
A control apparatus for a wind power installation is known from DE 368 799, the entire contents of which is incorporated hereby by reference, in which a self-excited and separately-excited generator are operated together with accumulators such that voltage is maintained automatically and the fluctuating power consumptions of the connected consumers are covered.
Known from EP 1 286 049 A2, the entire contents of which is incorporated hereby by reference, is a wind power installation having a stabilizing device which actively stabilizes the rotor in a low-load rotational position (park position). Additionally known is its own energy supply means, in particular in the form of an auxiliary wind power installation mounted on the machine gondola of the wind power installation.
Modern wind power installations frequently have an adjusting device, the so-called pitch drive, which can adjust the rotor blade about its longitudinal axis, thereby enabling an adjustment to different wind velocities.
If it becomes necessary to shut down such a wind power installation, the pitch drive brings the rotor blades into their flag position; i.e., the rotor blades are essentially positioned at right angles (90°) to their normal orientation. In this position, the rotor can be kept in a permanent standstill by a holding brake or by different stabilizing means. However, the rotor is frequently not kept at a standstill by a brake, instead the rotor spins in the wind; i.e., it rotates as thereby also does the drive train including the generator connected to the rotor, whereby the generator is disconnected from the power system. This condition is known as spinning mode. In this case, depending on wind velocity and direction, an irregular rotational speed of a few revolutions per minute commences, compared to the rotational speed in normal operation of the wind power installation being substantially higher, for example in the range of 15-20 revolutions per minute.
It is generally required for the rotor blades to be able to be set into the flag position also in the event of a power outage. For this purpose, energy stores are usually provided, for example accumulators or condensers for electrical pitch drives and accumulators for hydraulic pitch drives, which provide the power necessary for a one-time adjustment of the rotor blades into the flag position. Energy stores are frequently dimensioned such that they are depleted following this one-time displacement process and are not recharged until resumption of normal operation. DE 200 20 232 U1 proposes the use of an auxiliary generator in order to reliably rotate the rotor blades into the flag position.
For temporarily supplying the controller of the wind power installation in the case of power failure, a commercial, uninterruptible power supply (UPS) based on accumulators is usually provided, same being configured so as to supply the controller of the wind power installation with power for a short period of time so that, for example, a status signal can be sent via a remote monitoring system indicating that the operating system has been properly shut down and/or the controller switched off.
Required in the case of ocean (off-shore) wind power installations is that the wind power installations also be capable of supplying essential components with emergency power for several days or weeks in the event of longer power supply system outages. For this purpose, it is common to provide for a diesel generator, which must be supplied with an accordingly large quantity of diesel. Substantial maintenance costs are necessary to ensure a faultless state to the diesel and the diesel generator; among other things, the diesel must be continually or at least regularly recycled and replaced at specific intervals. The expenditure for this is substantial, in addition working with diesel fuel off-shore leads to environmental endangerment.
It is an object of the present invention to provide an emergency power supply in the event of power failure which can be produced at low expense, requires low maintenance in normal operation, and represents no danger to the environment.